Department Store Telescope

I have a Tasco department store telescope that I bought a few years ago, before I knew any better. It has a 76mm main mirror with a focal length of 700mm and uses the smaller .965" eye-pieces. Despite all that, I have managed to get some excellent views from it, including Jupiter and its Galilean moons, Saturn's rings and close-ups of our own Moon. However, the limitations are now starting to annoy me, but I'm unable to justify expenditure on a complete new scope. So I read a couple of pages on the web about basic improvements that can be made to get more out of a department store telescope. One area that seemed promising was the use of better eye-pieces, particularly the more standard 1.25" ones.

So I bought a 0.965" to 1.25" adapter and a nice 15mm Celestron 1.25" plossl eye-piece.

However, now when I fit the eye-piece adapter and the new eye-piece I can't bring the image into focus. Presumably this is because the eye-piece is sitting too far away from the secondary mirror with the eye-piece adapter in place? The eye-piece adapter is pretty small. It's just a straight through adapter, not a diagonal, and it's hard to imagine how it could be made any shorter.

I then purchased a 1.25" 2x Barlow to see if this would help. I justified this to myself by saying that these 1.25" items would be of use if I do eventually get a better scope! I'm now very close to being able to bring the image into focus, but it's still not quite there.

Is there anything else I can do? I know little or nothing about how the optics of these telescopes work, but it seems that I need to be able to either bring the eye-piece closer to the secondary mirror or else find some way of moving the focus point further back from the mirror. Any help would be greatly appreciated.

Welcome to the boards lphilp00! Like you, I also have a 3" reflector from Tasco that Santa brought me years ago. Its pales considerably to todays Tascos (no slow motion control equatorial mounts back then!), but still, I also got great views with it.

If your Tasco doesn't hold much value to you, you could get a proper cheap 1.25" focuser and actually DIY mount it, REPLACING the current 0.95" focuser. That would definitely give you better focus, and slightly better images.

Thats what I would do anyway as a short term solution prior to saving up some more for a larager scope.

Seanie.

Thanks for the reply and the welcome Seanie. I'd have no objection to trying this. Any idea where I might get a 1.25" focuser? Is this something that can be bought separately, or would it need to be found on an old second-hand scope?

Hi

Mayby you should consider stop spending more money on this Tasco and have a look around at upgrading. I see Greenwitch are having a January sale

www.greenwich-observatory.co.uk/acatalog...escope_Specials.html

I suspect that a 1.25 focuser is going to cost you a significant amount of money. I see a Meade DS-2070 AT 70mm for £149 goto and motor drive system.

If its gone at this point more are bound to come up at some point. I dont think spending money on a tasco is the answer. My " 2 cents" only though:)

lphilp00,

If the amount you need is only a small distance, you might be able to achieve this by moving the main mirror forward in the tube by loosening all three colminating screws behind the mirror by the same amount.

If this is not enough then you could possibly remount the main mirror further up the tube. I do not know how the mirror assembly is fixed in these telescopes so this may be easy or more difficult.

Failing that a change of focuser as Seanie said is the only other sollution. Just be sure that it is a low enough profile design to work.

Michael

Jeez you guys are helpful! Thanks for all the replies. I realise that I may have been starting to throw good money after bad, but as I said, the 1.25" accessories should serve me well on any future telescope. That offer from Green Witch looks a bit useful alright. Now I just have to persuade the boss/Missus! I might try loosening those collimating screws first. They could save me a few quid. Thanks again for your help everyone!